The author presents some laboratory data on the biology of Pseudococcus maritimu (Ehrhorn) a potato pest in Brazil. With the exception of the first instar larvae, there is a broad difference betweei males and females, in shape, development and behaviour. The female feed throughout the period of development, going through three instars. The lif cycle takes an average of 73 days. The number of eggs per female averages 323 The male feeds only during the first and part of the second instar, and develop thereafter in a cocoon, passing through four instars. The life cycle takes an averag of 41 days. The adult lives an average of 3.4 days while the female adult lives 3J days. It appears that this species does not reproduce by parthenogenesis. Pseudococcus maritimus is a species widely distributed over many countries, livini on numerous kinds of plants.